The present invention relates to a double-pipe heat exchanger for use as an EGR cooler, an oil cooler, or the like, the double-pipe heat exchanger being capable of smoothly bending along a pipeline of vehicles.
An EGR cooler is interposed on the way of piping of exhaust gas of an engine, and acts to cool the exhaust gas using cooling water. This EGR cooler is exemplified as below by a double-pipe heat exchanger disclosed in Japanese Patent Application Laid-open No. 2000-161871.
This double-pipe heat exchanger is in a double-pipe structure with an inner tube and an outer tube, in which structure a radiator fin is integrally formed by bending at the intermediate portion in an axial direction of the inner tube. That is, the inner tube has at the intermediate portion a multiple number of protrusions formed in a radial direction from the center in section thereof.
Conventionally, an EGR cooler is interposed at the linear portion on the way of piping for exhaust gas of an engine. Therefore, there have been such problems that the EGR cooler lacks flexibility in a position to be disposed, and the number of parts for connection thereof, for example, becomes big, thus inevitably resulting in higher manufacturing costs as a whole.
Accordingly, an object of the present invention is to provide a double-pipe heat exchanger in simple structure capable of being easily bent conforming with a pipeline, and a manufacturing method thereof.